Relatively complex planarization procedures are often required in the formation of devices having relatively wide trenches due to the fact that film material deposited by conventional chemical vapor deposition (CVD) processes typically covers the depression conformally, thus replicating the depression's non-planar structure.
Horng et al. in U.S. Pat. No. 4,211,582, issued Jul. 8, 1980, disclose relatively narrow silicon mesas in a relatively wide trench. These mesas are completely oxidized after formation. However, Horng et al. do not suggest that such mesas may be used in conjunction with the deposition of a conformal CVD oxide so as to prevent the formation of a relatively deep depression overlying the trench.
Schiltz and Pons ["Two-Layer Planarization Process", J. Electrochem. Soc. 133:178-181 (1986)] disclose the use of a plurality of vertically extending fingers in a trench which increase the distance the top surface of a conformal coating overlying the vertical fingers is spaced from the base of the trench. Schlitz and Pons do not suggest the use of such vertical finger structures as a means for avoiding the formation of a unitary deep depression in an oxide film overlying a wide trench.
A need thus exists for a method for planarizing over a recessed area of a semiconductor structure.